Metformin vs Insulin: side effects in FDA adverse event reports
At a glance
| Metformin | Insulin | |
|---|---|---|
| Drug class | – | Insulin Analog |
| Brand names | Metformin Hydrochloride | Insulin 1556 |
| FAERS reports | 354,745 | 55,432 |
| Serious | 69% | 78% |
| Death outcome | 29,950 | 7,568 |
| Boxed warning | Yes LACTIC ACIDOSIS Postmarketing cases of metformin-associated lactic acidosis have resulted in death, hypothermia, hypotension, and resistant bradyarrhythmias. Th | No |
Signals both drugs share
| Reaction | Metformin | Insulin | Label screen (A / B) |
|---|---|---|---|
| Hypoglycaemia | 7,287 · PRR 10.3 | 1,820 · PRR 14.7 | Labeled — boxed warning / No label text to screen |
| Diabetic ketoacidosis | 4,053 · PRR 11.9 | 995 · PRR 16.3 | Labeled adverse reaction / No label text to screen |
| Diabetes mellitus inadequate control | 2,895 · PRR 11.4 | 729 · PRR 16.2 | Labeled (related wording) / No label text to screen |
| Euglycaemic diabetic ketoacidosis | 1,754 · PRR 46.1 | 85 · PRR 8.2 | Labeled (related wording) / No label text to screen |
| Ketoacidosis | 1,347 · PRR 12.8 | 255 · PRR 13.3 | Labeled adverse reaction / No label text to screen |
| Diabetic metabolic decompensation | 469 · PRR 29.9 | 54 · PRR 15.3 | Labeled (related wording) / No label text to screen |
| Hyperkalaemia | 3,924 · PRR 7.4 | 693 · PRR 7.6 | Not in label — unassessed / No label text to screen |
| Diabetic neuropathy | 670 · PRR 9.0 | 206 · PRR 16.3 | Likely indication confounding / No label text to screen |
| Hypoglycaemic coma | 508 · PRR 12.4 | 63 · PRR 8.4 | Not in label — unassessed / No label text to screen |
| Diabetic retinopathy | 389 · PRR 7.5 | 166 · PRR 19.4 | Likely indication confounding / No label text to screen |
| Hyperparathyroidism secondary | 295 · PRR 7.7 | 48 · PRR 7.3 | Not in label — unassessed / No label text to screen |
| Pancreatic carcinoma metastatic | 287 · PRR 6.5 | 54 · PRR 7.3 | Not in label — unassessed / No label text to screen |
Labeled signals distinctive to Metformin
- Acute kidney injury — n=17,231, PRR 7.4 Labeled — boxed warning
- Lactic acidosis — n=17,141, PRR 67.6 Labeled — boxed warning
- Metabolic acidosis — n=6,200, PRR 14.2 Labeled adverse reaction
- Vitamin b12 deficiency — n=630, PRR 10.8 Labeled (related wording)
- Anion gap increased — n=243, PRR 12.9 Labeled (related wording)
Labeled signals distinctive to Insulin
- None stood out among the strongest labeled signals.
Common questions
Which has more reported side effects, Metformin or Insulin?
Metformin has 354,745 FAERS reports and Insulin 55,432. More reports does not mean more dangerous: volume follows how widely and how long a drug has been used, prescription vs over-the-counter status, and publicity. The seriousness share (69% vs 78%) is a better like-for-like signal of the kind of problems reported.
Which side effects do Metformin and Insulin share?
Both drugs carry disproportionality signals for hypoglycaemia, diabetic ketoacidosis, diabetes mellitus inadequate control, euglycaemic diabetic ketoacidosis, ketoacidosis. Shared signals often reflect a shared drug class or the condition both are used for.
Is Metformin or Insulin safer?
FAERS cannot answer that: it has no denominator and no comparator. Use this page to see which risks are already on each label and which signals are unlabeled, then check the prescribing information and your clinician for your situation.
Sources: openFDA FAERS pair statistics (OpenPV build 2026-09-14), FDA labels via openFDA, openFDA count queries for seriousness and deaths. Pair chosen because it is a commonly searched comparison. Generated 2026-10-08.